1. Field
One embodiment of the present invention relates to an optical integrator, illumination optical apparatus, exposure apparatus, and exposure method and, more particularly, to an optical integrator suitably applicable to an illumination optical apparatus in exposure apparatus for manufacturing micro devices, such as semiconductor devices, image pickup devices, liquid-crystal display devices, and thin-film magnetic heads, for example, by lithography.
2. Description of the Related Art
In the typical exposure apparatus of this type, a light beam emitted from a light source is guided through a fly's eye lens to form a secondary light source consisting of a large number of light sources on the rear focal plane of the fly's eye lens. Light beams from the secondary light source are guided through an aperture stop disposed in the vicinity of the rear focal plane of the fly's eye lens, to be limited thereby, and then enter a condenser lens. The aperture stop limits the shape and size of the secondary light source to a desired shape and size, according to a desired illumination condition (exposure condition).
The light beams condensed by the condenser lens illuminate a mask with a predetermined pattern therein, in a superposed manner. Light transmitted by the pattern of the mask travels through a projection optical system to be focused on a wafer. In this manner the mask pattern is projected (or transferred) onto the wafer to effect exposure thereof. The pattern formed in the mask is of high integration and a uniform illuminance distribution must be formed on the wafer in order to accurately transfer the microscopic pattern onto the wafer. One of the known exposure apparatus having such a configuration is, for example, the exposure apparatus described in U.S. Pat. No. 6,738,129.
An object of the present invention is to provide an optical integrator with characteristics to suppress the influence of relative positioning error of a plurality of optical members on the illuminance distribution and on the shape of the illumination field.
Another object of the present invention is to provide an illumination optical apparatus with high performance capable of illuminating a surface to be illuminated, under a desired illumination condition, using an optical integrator with less influence of relative positioning error of a plurality of optical members on the illuminance distribution and on the shape of the illumination field.
Still another object of the present invention is to provide an exposure apparatus and exposure method capable of performing good projection exposure under a good illumination condition, using an illumination optical apparatus with high performance adapted to illuminate a surface to be illuminated, under a desired illumination condition.